SPHENOPHRYNE - American Museum of Natural History
SPHENOPHRYNE - American Museum of Natural History
SPHENOPHRYNE - American Museum of Natural History
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102 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 253<br />
Fig. 58. SEM photograph <strong>of</strong> palatal folds <strong>of</strong><br />
Liophryne rhododactyla BPBM 9793, anterior to<br />
top <strong>of</strong> figure. Scale line spans 2 mm.<br />
FRONTOPARIETALS: In most species these<br />
are somewhat parallel-sided bones, flaring<br />
posteriorly and in some with lateral margins<br />
converging slightly anteriorly (figs. 66–68).<br />
Exceptions are A. blumi, A. gracilipes, and<br />
A. novaebritanniae, in which the lateral margins<br />
diverge gradually before flaring (see<br />
Zweifel, 1985b: fig. 45, for gracilipes).<br />
There is considerable interspecific variation<br />
in the width <strong>of</strong> the braincase relative to the<br />
width <strong>of</strong> the skull, with the ratio ranging<br />
from 0.209 to 0.455. Two small species, A.<br />
gracilipes (0.429) and A. novaebritanniae<br />
(0.444), and Sphenophryne cornuta (mean<br />
0.376 [0.336–0.455], N 3) have the widest<br />
braincases. The frontoparietal region is unusually<br />
short in cornuta where the ratio <strong>of</strong><br />
braincase length to skull length averages<br />
0.559 (0.526–0.580, N 3). The lowest such<br />
ratio in all other specimens is 0.631 in one<br />
<strong>of</strong> five Oxydactyla stenodactyla.<br />
PREMAXILLAE: The premaxillae <strong>of</strong> 15 species<br />
are illustrated in figures 63 and 64,<br />
where ventral views emphasize the shape <strong>of</strong><br />
the premaxillary shelf. Interspecific variation<br />
in the shelf involves its length (relative to the<br />
width <strong>of</strong> the bone) and the degree <strong>of</strong> emargination<br />
<strong>of</strong> the posterior edge. The relatively<br />
longest bones are seen in O. alpestris and O.<br />
stenodactyla, with O. coggeri approaching<br />
these two in length. The first two also show<br />
the least emargination. Inasmuch as these<br />
(and coggeri) are secretive species and probably<br />
are head-first burrowers in litter and<br />
grass clumps, the relatively robust bones may<br />
serve a strengthening function.<br />
Another variable in premaxillae is the extent<br />
to which the ascending process slopes<br />
forward. In species with snouts that project<br />
notably beyond the lip, such as A. palmipes<br />
and A. rivularis, the ascending process is<br />
conspicuous in ventral view, whereas processes<br />
that are essentially vertical cannot be<br />
seen (O. alpestris, O. coggeri). The variation<br />
shown in the drawings should not be taken<br />
Fig. 59. SEM photographs, enlarged views <strong>of</strong> conical projections <strong>of</strong> posterior palatal fold shown in<br />
fig. 58. Left scale line spans 100 m, right 20 m.